Our most important source of radiant energy is, of course, the sun. Without it there would be no life, for plant life depends upon radiant energy-and we depend upon plant life.

• 当然，我们人类最重要的光能的来源就是太阳。没有太阳，就没有生命，植物的生命依赖辐射能，而我们依赖植物的生命。